- #71
The Electrician
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The center frequency stays the same, but the rolloff rate is enough higher to meet your requirements. Unity remains at 10 kHz.
BiGyElLoWhAt said:So would both my lowpass filters have the same RC values?
BiGyElLoWhAt said:Yes, yes. I think I get it now. What would be a reasonable, physical approximation that I could use to get my values? I.e. how I was trying to maximize it at 10k by setting both circuits in phase with each other and they would maximize due to superposition or something along those lines, or as was mentioned early where z_1 = R_1 at 3k, etc.
BiGyElLoWhAt said:What's a reasonable threshold to call something at "unity"? I think I get what I need to do, now. Thanks.
BiGyElLoWhAt said:But that's only theoretical, right? You can't actually get the gain to be 1.
Have you determined the Q with those component values?The Electrician said:Here's the un-normalized response of your original circuit using the R and C values I gave in post #25:
I have been wanting to reconcile this equation with the plot in #25. Is there an error in this apart from the subscript?donpacino said:when analyzing the circuit, the transfer function is found seen below
Vo/Vin = [SC_2R_2 ] / [ S^2C_2^2R_2_2+S(2C_2R_2+C1R1)+1 ]
Just checked my work. Yes it is incorrect. I now got what the electrcian got. I switched some terms part way through the analysis. 1 am algebra will do that I guess.The Electrician said:donpacino in post #32 has the wrong transfer function. The pdf file in post #60 has the derivation of the correct transfer function.
My derivation is the same:
View attachment 106821
The figure of 0.33 does seem lower than what I would expect to be achievable.NascentOxygen said:With the Rs and Cs suggested, I calculate using your equation: Q = 0.333